Screening device



Oct. 29, 1940. J. s Y 2,219,453

SCREENING DEVICE Filed Sept. 2, 1958 Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE Claims.

The invention relates to screening device for the separation of finer from coarser material.

Its objects are to provide a device of this nature which shall be of high eiflciency both in screening 5 out the finer particles, delivering the separate grades to separate bins and to utilize the air .which has already passed through the device by withdrawing it from a receiving and settling chamber below the screen and forcing it again through the screening chamber, together with newly entering unscreened material.

. The invention is embodied in a device such as hereinafter described and as shown in the accompanying drawing, in which Fig. 1 is a central longitudinal section of the apparatus, the return passage for the air being indicated diagrammatically;

Figs. 2, 3 and 4, are transverse sections respectively, on the lines 2-2, 3-3 and l-4.

The body of the apparatus is cylindrical in shape and formed of sheet metal, as indicated at H), the ends of this cylinder being out-turned at right angles, as indicated at ll, [2 and fixed against and suitably secured to angular flanges as [3, 14 formed on the head and base of the device which are preferably of cast metal. A cylindrical screen I5, of any desired mesh, is secured to annular flanges l6, IT. The screen is spaced a sufficient distance from the wall I0 to provide a suitable annular chamber for the reception of the fine material and its delivery into a suitable outlet. The upper end of the apparatus is of cast metal and consists of an end plate 18 and an annular wall l9 from the lower end of which the flange [3 projects. The side wall I9 is provided with a tangential nipple 20 to which a charging pipe section 2| is attached which pipe section receives the material through a valvecontrolled hopper 22.

The base of the device is a casting comprising an annular flange I4 upon which the flange of the cylinder I0 is seated and to which it is secured in any desired manner. The outer wall of this base casting extends downwardly a short distance in cylindrical form, as indicated at 24, and thence tapers downwardly and laterally, as indicated at 25, its lower end being flanged as shown at 26 for attachment to a suitable receptacle.

From the inner margin of the flange M a tapering chamber 21 for receiving the coarser material descends a short distance and terminates in the conveying pipe 21a which passes through the wall 25 of the chamber into which the finer material is delivered from the screen.

An air chamber 28 surrounds the tapering receptacle for the coarser material and is enclosed by the wall of said chamber and an outer wall 29 which is suitably spaced from the wall of the outlet for the screened material, the two walls of the air chamber being united at their upper margins and spaced apart below, forming a connectionbetween the air receiving chamber 28 and the receiving chamber for the fine material enclosed by the wall 24 and its extension. The chamber 28 being relatively more commodious than the outlet from it, the movement of air through it is comparatively slow and the precipitation of solids therefrom is substantially complete.

A nipple 30 leads laterally from the chamber 28 and with it is connected an air pipe 3| leading to the receiving opening of a fan blower 32 which delivers through a pipe 33 to the receiving nipple 2| for the material to be operated upon.

Preferably the nipple 30 leading from the air chamber and the pipe leading from said nipple are of greater capacity than the delivery pipe 33 of the blower.

Efiiciency is enhanced if the density of the material is maintained approximately uniform over the entire area of the screen. This is approximately secured by giving the inner chamber of the structure an annular form of gradually diminishing radial dimension as by the following means.

A circular partition 34 depending centrally from the cap [8 extends approximately to the lower end of the screen I5 and preferably flares somewhat from its upper portion downwardly, providing with the screen an annular passage for the material, of gradually diminishing radial dimension. As the material enters through the tangential nipple 20 it strikes forcibly against the solid side wall of the cap 18 and is somewhat scattered and deflected downward but follows the surface of the screen because of the centrifugal force. The scattering of the larger particles above referred to prevents impacting of the material against the screen, permitting the free passage therethrough of the fines. "The gradual increase of the diameter of the member 34 toward its lower end decreases the cross area of the passage within the screen roughly as the volume of the air and material within the screen decreases and thus tends to maintain the velocity of movement of the material. The diameter of the lower end of the member 34 while restricted is still ample to permit the escape in to the chamber 21 of all of the coarser material.

The capacity and efliciency of the apparatus are materially increased by the use of a circula ing pump the receiving side of which is in communication with the lower end of the chamber into which the screen delivers. A minus pressure in that chamber will reduce the pressure at the opposite side of the screen and insure an expelling air current throughout the entire mass of the material being passed through the apparatus.

An enlargement of the intake pipe of the pump into a comparatively commodious chamber, 28, will greatly reduce the percentage of the fines that will be carried through the pump.

While a highly efficient form of construction is disclosed, various changes may be made Within the scope of the appended claims.

I claim as my invention:

1. A screening device comprising in combination, a vertical body having a tangential receiving port, a cylindrical screen within and of less diameter than the body, a conduit leading from the lower end of the body, a funnel-shaped conduit leading from and fitting the lower end of the screen and delivering independently of the first-named conduit, a skirt depending from the upper end of second-named conduit and spaced from the tapering portion thereof, and an air pump receiving from the chamber enclosed by the skirt and delivering to the receiving port.

2. In a screening device, in combination, a chambered body having tangential receiving opening near its upper end, a cylindrical screen dividing the chamber Vertically into two compartments having individual outlets, and separating the outer compartment from the receiving opening, an air pump discharging into the receiving opening, an open bottomed settling chamber communicating with the discharge outlet for the screened material from the compartment separated from the receiving opening and a duct connecting the settling chamber with the inlet port of the pump.

3. A screening device comp-rising in combination a vertical body having a closed top and a tangential receiving port, a cylindrical screen within and spaced from the side walls of the body, the chamber between the screen element and such walls being closed at the top, an annular conduit leading from the lower end of such chamber, a funnel-shaped conduit leading from and fitting the lower end of the screen, a skirt depending vertically from the upper end of the second named conduit, its lower portion being parallel with the tapering portion thereof, and an air pump receiving from the chamber enclosed by the skirt and delivering to the receiving port.

4. In a screening device comprising a vertical cylindrical screen element and an enclosing cylindrical casing therefor having a closed upper end and being spaced from the screen element, the chamber between the screen element and the side walls of the casing being closed at the top and being open at the bottom for the discharge of the fine material entering the chamber through the screen, the casing having a tangential receiving port delivering to the chamber of the screen element, the combination with such elements, of a central circular imperforate core spaced from the screen element and depending from the end of the casing approximately to the lower end of the screen element and being flaring in its lower portion, and providing with the screen element an annular discharge opening for coarser material.

5. In a screening device, in combination, a vertical cylindrical casing having a closed top, a cylindrical screening element within the casing and spaced from the side walls thereof, the intervening space being closed at the top and open at the bottom, a, tangential receiving port in the side wall of the casing delivering to the chamber of the screen element, an imperforate core co -axial with and. spaced from the screen element and extending approximately to the lower end there of and forming with such end an annular discharge port for the coarser material.

' ALFRED J. MOSLEY. 

